The invention relates to the use of a holding device for a spectacle lens for the purpose of inserting and removing the spectacle lens into or from a container and/or of mounting and removing it on or from a spectacle lens holding shaft of a spectacle lens edge processing machine by means of a handling apparatus.
Such a holding device is described in conjunction with a system for processing the circumferential edge and/or an optical surface of spectacle lenses in DE 44 14 784 C2 of the same applicant. In the case of this system, a blank is initially inserted by means of a handling apparatus into an optoelectronic detecting device which has an electronic image processing and evaluation system for detecting customary markings such as dots, crosses and notches at the edge of the blank, or the position of an adjacent part. The electronic image processing and evaluation system of the optoelectronic detection device transmits signals to a control device for the handling apparatus, such that the blank can be inserted accurately in position by means of the handling apparatus into a holder, in particular a spectacle lens holding shaft of a spectacle lens edge processing machine.
In order to manipulate the blank, the handling apparatus has a movable holding device with a single sucker for inserting the blank into the detecting device, and several suckers arranged arcuately for the purpose of transferring the blank from the detection device into the spectacle lens edge processing machine. The suckers are arranged in this case on an annular segment which can be rotated relative to the holding device and whose rotation axis is perpendicular to the individual suckers. The arcuately arranged suckers can be used to grip a blank in the region of the edge and transfer it from a three-point support of the optoelectronic detecting device onto or into the spectacle lens holding shaft of the spectacle lens edge processing machine, the middle region around the optical axis of the blank remaining free for the purpose of attaching the soft elastic head on the swivel arm of the optoelectronic detecting device, or of inserting it into the spectacle lens holding shaft in the spectacle lens edge processing machine.
Underpressure can be applied to the suckers for the purpose of holding the blank. The central sucker on the holding device serves the purpose of removing a blank from a container and placing it onto the three-point support of the optoelectronic detecting device, while the suckers arranged on the annular segment grip from above or from below a spectacle lens blank lying on the three-point support, and insert it into the spectacle lens holding shaft, as a result of which it is ensured that no impediment can arise from the guide rod with the soft elastic head or from the spectacle lens holding shaft. It is also mentioned, however, that a blank can also be inserted by means of the central sucker into the spectacle lens holding shaft when it is ensured that the blank is initially held on one side on the spectacle lens holding shaft, and when the spectacle lens holding shaft can be moved apart to such an extent that the holding device can be moved into this region and a blank can also be inserted by means of this sucker.
It is the object of the invention to create a holding device which is suitable for holding a spectacle lens by means of a central sucker and for inserting it into a spectacle lens holding shaft with positional accuracy, in particular with axial accuracy with reference to the optical surface of the blank opposite the holding device, the aim being for this holding device to be fashioned such that it can be used with conventional spectacle lens edge processing machines whose spectacle lens holding shaft does not need to be adapted to the holding device.
Starting from this formulation of the problem, it is proposed to use a holding device which comprises a base which is held by the handling apparatus and has a depression, a controllable vacuum-pressure connection at the depression, and a spherical cap which is arranged in the depression, bears tightly against an annular surface of the depression and has an opening to the depression and a sealing region at the edge of the spherical cap for the purpose of bearing against an optical surface of the spectacle lens in order to insert and remove the spectacle lens into or from a container and/or for the purpose of being mounted and removed on or from a spectacle lens holding shaft in a spectacle lens edge processing machine by means of a handling apparatus which holds the base.
If, with the vacuum pressure not applied, the spherical cap is placed onto an optical surface of a blank, it is adapted to any desired angular position of this optical surface, while the opposite optical surface maintains its position. If the vacuum pressure is applied, the blank is held in the sealing region at the edge of the spherical cap, while the spherical cap is drawn against the annular surface of the depression in the base and is held in this position owing to the friction between the annular surface of the depression and the complementary surface of the spherical cap. If, by means of the handling apparatus, the blank is now brought between the separated halves of a spectacle lens holding shaft in a spectacle lens edge processing machine, the blank can be positioned with its free surface accurately in position and precisely coaxial with the axis of this spectacle lens holding shaft, and be fastened there in a suitable way. This can be performed in such a way that the blank is moved with the free optical surface directly against a clamping sleeve, to which vacuum pressure can be applied, on this half of the spectacle lens holding shaft, and is held by the application of vacuum pressure. It is possible furthermore, to provide the optical surface, opposite the holding device, of the blank in a centering device with a conventional block or sucker which can be inserted accurately in position and coaxially in a corresponding clamping sleeve on the corresponding half of the spectacle lens holding shaft. In this case, as well, it is possible in addition to apply vacuum pressure to the clamping sleeve in order to increase the holding force. After the blank has been mounted on one half of the spectacle lens holding shaft, the vacuum pressure of the spherical cap is neutralized, the holding device is moved out of the region of the spectacle lens holding shaft, the second half of the spectacle lens holding shaft is pressed against the now free optical surface of the blank, and the edge processing can begin.
The annular surface of the depression in the base can be designed so as to yield a linear contact of the surface of the spherical cap. In order to improve the sealing effect, and reduce the areal pressure occurring in this region owing to the application of vacuum pressure, it is advantageous for the annular surface of the depression to be designed as a spherical surface complementary to the spherical cap. The spherical cap can advantageously be movably fastened on the base by means of a mushroom-shaped holder guided through the opening so that it cannot be lost when the application of vacuum pressure is neutralized.
The spherical cap can be produced overall from an elastic synthetic material, but preferably has a soft lip seal in the sealing region, thus ensuring good adaptation to and sealing on a nonspherical optical surface of the blank. The dimensions of the base with the spherical cap arranged therein are only negligibly greater than those of a conventional block or sucker, with the result that the holding device according to the invention can be moved without difficulty with a blank into the region of the separated halves of the spectacle lens holding shaft. If the base is enlarged or lengthened in the shape of a plate on at least one side, a retaining bolt can be arranged at an edge region for the purpose of fastening on the handling apparatus. This eccentric arrangement of the retaining bolt ensures that the region of the spectacle lens holding shaft remains completely free of elements of the handling apparatus.
The plate-shaped design and the arrangement of a retaining bolt in the edge region is also associated with an advantageous guidance of the vacuum-pressure connection which can be guided in the form of bores from the depression through the plate-shaped enlargement of the base and the retaining bolt.